1. Summary of the Invention
This invention relates generally to securing communication links between a computer and a remote terminal and more particularly to a system for accessing a computer and keying an encryption network for data transmission through pseudorandom number generation.
Society's multifaceted dependency upon computer systems has increased the possible effects of unauthorized computer access to untold levels. Computer networking, such as time sharing systems, has led to inherent security problems, since programs executed by such systems shared access and cooperated with each other. The capabilities of recent computer systems included not only the utilization of remote terminals but extensive resource sharing and batch processing of different projects. The use of such systems has necessarily increased the likelihood of deliberate or even accidental acquisition and/or alteration of data.
Computer systems have been subject to a variety of security risks ranging from misappropriation of confidential data through unauthorized use of computing time. Access controls have been used in virtually all time sharing and most other computer systems. Differences in the nature of the information being processed have given rise to various security measures and procedures commensurate with the value attached to such data and the consequences of unauthorized access and/or appropriation thereof. For example, the data processed in computer systems utilized for financial transactions has a substantial value due to the monetary losses which could be sustained as a result of system penetration.
A user has been traditionally identified by at least one of the following:
(a) through something he knew or had memorized, e.g. a password; PA1 (b) through something he carried wih him, e.g. a card or badge; or
(c) through a personal physical characteristic, e.g. recognition by a guard.
Passwords have been widely employed to authenticate a remote terminal user. The use of passwords has been augmented by secondary security measures in many instances. For example, a typical consumer banking terminal accesses its computer by using a combination of a magnetically encoded card and the user's memorized password commonly referred to as a personal identification number.
While such systems might have been satisfactory from a cost/loss risk standpoint, they were subject to penetration with or without access to the individual user's card. Various password selection procedures and their susceptibility to penetration have been discussed in a U.S. Department of Commerce publication entitled The Use of Passwords for Controlled Access to Computer Resources, NBS Special Publication 500-9 dated May 1977.
In addition to penetration of the user's password, passwords themselves were ineffective, for example, against the penetration threat of between-lines entry and piggy-back infiltration. Unauthorized interception of communication links between the computer and a remote user has been a further security problem and resulted in obtaining not only the data transmitted but the user's password for subsequent access.